Update Code to 1.90.0 (#6824)

Additionally:

- Update Node to 20.11.1
- Update documentation
- Disable extension signature verification

This works around an issue where the Open VSX is not returning the
expected zip.  Verification is skipped later anyway because
@vscode/vsce-sign is missing in the OSS version.

flake.nix

@@ -7,7 +7,7 @@
     flake-utils.lib.eachDefaultSystem
       (system:
         let pkgs = nixpkgs.legacyPackages.${system};
-            nodejs = pkgs.nodejs-18_x;
+            nodejs = pkgs.nodejs_20;
             yarn' = pkgs.yarn.override { inherit nodejs; };
         in {
           devShells.default = pkgs.mkShell {